Cryogenic tank assembly with a pump drive unit disposed within fluid storage vessel

ABSTRACT

A fluid storage and pressurizing assembly includes a storage receptacle and a pump assembly. The storage receptacle includes an inner vessel defining a cryogen space for storing a fluid at a storage pressure and a cryogenic temperature, an outer vessel surrounding the inner vessel, and an insulated space between the inner vessel and the outer vessel, and a pump assembly. The pump assembly includes a pump immersed in the cryogen space having an inlet for receiving a quantity of fluid from the cryogen space, and an outlet for delivering the fluid therefrom. The pump assembly further includes a pump drive unit for driving the immersed pump, the pump drive unit being at least partially disposed within a space defined by the storage receptacle.

TECHNICAL FIELD

The present application relates to a cryogenic tank assembly, and moreparticularly to a cryogenic tank assembly having both a pump and a pumpdrive unit disposed within a storage vessel.

BACKGROUND

Developments in combustion engine technology have allowed for the use ofgaseous fuels instead of diesel as a fuel, without sacrifices tovehicular performance or delivery. As used herein, gaseous fuels aredefined as those fuels that are in the gas phase at standard temperatureand pressure, which in the context of this application is 21 degreesCelsius (° C.) and 1 atmosphere (atm). Exemplary gaseous fuels includenatural gas, methane, hydrogen and other combustible hydrocarbonderivatives. Because of its ready availability, low cost and potentialfor reducing particulate emissions, natural gas is increasingly used asthe gaseous fuel of choice, to fuel a range of industrial and vehicleengines, including mine trucks, locomotives, ships and other heavy goodsvehicles (HGVs). To increase the energy density of natural gas storage,especially on vehicles, liquefied natural gas (LNG) is an attractivesolution compared to compressed natural gas (CNG) because of the higherenergy density that can be achieved at much lower storage pressures.

Natural gas fuelled direct injection engines that can deliver similarperformance profiles to diesel engines require the fuel to be deliveredto the engine at high pressures, to overcome the in-cylinder pressurefor late-cycle injection. In addition, a storage vessel for storing acryogenic fluid, such as LNG must be adequately thermally insulated tomaintain the stored LNG at cryogenic temperatures. Cryogenictemperatures are defined herein to be temperatures at which gaseousfuels will remain in liquefied form at a predetermined storage pressure.

Thermal insulation prevents heat transfer from the surroundingenvironment to the cryogen space within the storage vessel, because heatentering the cryogen space can cause the LNG to boil, increasing thevapor pressure within the vessel. If the vapor fluid pressure exceeds apredetermined pressure limit, to prevent any damage to the storagevessel, fuel pump or any other parts of a cryogenic tank assembly, apressure relief valve is triggered to vent vapor from the cryogen space.It is undesirable to vent vapor from the cryogen space, so in additionto the thermal insulation, conventional cryogenic tank assemblies alsoavoid locating anything inside the storage vessel that can introduceheat into the cryogen space. The applicant has patented some inventivecryogenic tank assemblies that do place a pump inside the cryogen spacewith a hydraulic pump drive located outside the storage vessel, forexample U.S. Pat. No. 7,293,418 B2. The temperature of hydraulic fluidemployed by the hydraulic pump drive can be in the range of 65° C. and90° C., and when compared to a typical temperature for LNG of on theorder of −160° C. forms a very large temperature gradient therebetween.In addition to the challenge of preventing heat from entering thecryogen space, there are other challenges associated with locating apump drive unit inside the storage vessel, such as preventing thefreezing of hydraulic fluid lines if the drive unit is a hydraulic driveunit.

Accordingly, there is a need for an improved cryogenic fuel storage andpressurizing assembly suited for large-scale cryogenic storage vessels,that increases the fuel storage volume within the designated fuelstorage space on board the vehicle, while mitigating the challengesassociated with locating a hydraulic pump drive unit within thecryogenic fuel storage and pressurizing assembly.

SUMMARY

The claimed system is a fluid storage and pressurizing assembly thatincludes a storage receptacle with an inner vessel defining a cryogenspace capable of storing fluid at a cryogenic temperature and a storagepressure, an outer vessel surrounding the inner vessel, and an insulatedspace between the inner vessel and the outer vessel. The entire cryogenspace is thus defined by the inner vessel and surrounded by theinsulated space. The insulated space can be evacuated to create a vacuuminsulated space.

The inner vessel and outer vessel further include a sleeve, whereby thesleeve of the outer shell extends within the sleeve of the inner vesselinto the cryogen space, with the insulated space extending the sleeve ofthe outer vessel and the sleeve of the inner vessel.

The storage and pressurizing assembly also includes a pump assembly toreceive the cryogenic fluid from the cryogen space and deliver ittherefrom. Specifically, the pump assembly includes a pump with an inletdisposed within the cryogen space, and an outlet for delivering thefluid to an accumulator or other pressurized-fluid receiving device. Thepump assembly also includes a pump drive unit, at least partiallydisposed within a space defined by the storage receptacle. The pumpdrive unit controls the pump such that the fluid received and deliveredby the pump is in response to the engine needs.

The pump drive unit is disposed within the storage receptacle such thatthe pump drive unit is at least partially recessed within the sleeve ofthe outer vessel. In exemplary embodiments, the pump drive unit is fullyrecessed within the sleeve of the outer vessel, and is disposed betweenthe cryogen space, as defined by the inner vessel.

The pump assembly is disposed within the storage receptacle such thatthe pump is immersed in the cryogen space, which allows the pump to bein a continuously cooled down state, and the pump drive unit issubstantially disposed within the sleeve of the outer shell.

In an exemplary embodiment, the pump is a reciprocating piston pump,with at least one piston disposed within the pump cylinder, and iscapable of pressurizing the fluid to a pressure between 2500 pounds persquare inch (psi) and 9500 psi. The reciprocating piston pump ispreferably actuated by a hydraulic drive unit.

The hydraulic drive unit comprises a hydraulic cylinder and a pistonreciprocable therein, and a drive shaft connected with the pistonextending out of the hydraulic cylinder for actuating the pump and ahydraulic fluid weep line associated with the drive shaft for collectinghydraulic fluid leaking from the hydraulic cylinder along the driveshaft.

Because the presently claimed system locates the pump drive unit withinthe inner vessel, the traditional configuration of the weep line is suchthat the weep line would be exposed to the cryogenic temperatures withinthe storage receptacle. The fluid in the weep line is thus susceptibleto freezing at these temperatures, which is undesirable. In exemplaryembodiments, the hydraulic weep line is associated with an endplate ofthe hydraulic cylinder, proximate to the pump, and is nested within oneof a first hydraulic fluid line or a second hydraulic fluid line. Theweep line is thus insulated from the cryogenic temperatures within thestorage receptacle; by nesting the weep line within the hydraulic fluidline, the continuous flow of warm fluid within the hydraulic fluid lineswill reduce freezing within the weep line.

In alternate embodiments, various other drivers can be used to drive thereciprocating piston. By way of example, these may include electricmotors, mechanical drive units, pneumatic drive units, or any otherdrive unit that doesn't depart from the spirit of the presently claimedsystem.

In yet another alternate embodiment, the pump drive unit is surroundedby thermal insulation, to ensure that the cryogenic temperature withinthe cryogen space does not affect the performance of the pump driveunit, and to reduce the heat leak from the pump drive unit into thecryogen space, which may raise the temperature of the fluid and causesome of it to turn to vapor. The thermal insulation may include anaerogel jacket, or any other suitable insulation.

In an exemplary embodiment, the fluid storage and pressurizing assemblyis intended for use with liquefied natural gas (LNG) or any othercryogenic fluid suitable for use as a vehicular fuel. The storage andpressurizing assembly is further intended for use on board heavy dutyvehicles including mine haul trucks with a storage volume of up to 2000US gallons and other heavy goods vehicles (HGVs).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a vehicle with the gaseous fuel storageassembly shown.

FIG. 2 is a cross sectional view of a cryogenic fluid storage andpressurizing assembly that includes a storage receptacle and a pumpassembly, with a pump drive unit of the pump assembly located within thestorage receptacle

FIG. 3 is cross sectional view of a hydraulic drive unit, with ahydraulic weep line disposed within a hydraulic fluid line.

DETAILED DESCRIPTION

Throughout the following description, specific details are disclosed toprovide a more thorough understanding of the claimed system. However,some well-known elements have not been shown or described in detail toavoid obscuring the presently disclosed system. Accordingly, thespecification and drawings are to be regarded in an illustrative, ratherthan restrictive, sense. The drawings are not to scale.

With reference to FIG. 1, vehicle 100 is shown with enclosure 102,located on vehicle chassis 104, and between wheels 106. Space 103defines at least the vertical space available for a cryogenic-fuelstorage receptacle, and can be defined at least partially by enclosure102. Vehicle 100 is, in an exemplary embodiment, a large heavy goodsvehicle, however the vehicle can be understood to be any vehicle with anon-board tank assembly for storing cryogenic fuel. There is limitedspace available for the cryogenic fuel storage assembly, and the shapeof conventional prior art cryogenic storage receptacle 108 with pumpdrive unit 110 located external to storage receptacle 108 results inempty space 112 extending annularly around the pump drive unit, withinenclosure 102. Thus the presently claimed system aims to provide a morecompact arrangement for increasing the volume of fuel that can be storedwithin the available enclosure 102, by locating pump drive unit 110within cryogenic storage receptacle 108, such that empty space 112 isincorporated as part of the available fuel storage volume of cryogenicstorage receptacle 108, as shown by outline 114. Outline 114 thusrepresents the total space available for cryogenic storage fuel storagewhen pump drive unit 110 is located within cryogenic storage receptacle108, which is greater than that available when pump drive unit islocated external to cryogenic storage receptacle 108.

Generally, the presently claimed system relates to a cryogenic fluidstorage and pressurizing assembly that includes a storage receptaclewith a cryogen space capable of storing fluid at a cryogenic temperatureand at a storage pressure within a predetermined range, and a pumpassembly. The pump assembly includes a pump for receiving the cryogenicfluid and delivering it to a user at a higher pressure, and a pump driveunit to drive the pump. In exemplary embodiments, both the pump and thepump drive unit are fully disposed within the storage receptacle,resulting in a more compact arrangement such that the storage receptacleincorporates the empty space that would conventionally surround it, thusincreasing the total available cryogenic fluid storage volume. For otherapplications, such as rail tender cars, the storage receptacle diametercan be made larger while maintaining the same overall height because thepump drive unit need not extend above the level of the storagereceptacle. While it is already known to locate a pump inside thestorage receptacle, locating the pump drive unit inside a storagereceptacle for fluids stored at cryogenic temperatures is morechallenging. When exposed to cryogenic temperatures within the storagereceptacle, a pump drive unit may freeze up and be rendered inoperative.The pump drive unit thus needs to be insulated from the cryogenictemperature within the storage receptacle. Pump drive units aregenerally known to be a source of heat when in use, thus adequateinsulation is also needed to prevent heat generated in the pump driveunit from being transferred into the cryogen space, which may heat upthe cryogenic fluid, transforming it into vapor. This increases thepressure within the storage receptacle, and may eventually need to bevented to prevent damage to the cryogenic tank assembly, which isundesirable. The cryogenic fluid storage and pressurizing assembly canbe used to store and pressurize LNG) or any other cryogenic fluidsuitable for use as a vehicular fuel. The storage and pressurizingassembly can be used on board heavy duty vehicles including mine truckswith a storage volume capacity up to 2000 US gallons, and other HGVs.

With reference to FIG. 2, cryogenic fluid storage and pressurizingassembly 200 is shown, with storage receptacle 202 and pump assembly204. Storage receptacle 202 comprises inner vessel 206 which defines theboundaries of cryogen space 203, and outer vessel 208. Inner vessel 206and outer vessel 208 are separated by insulation space 210, which may beevacuated to provide thermal insulation, to insulate cryogen space 203from outer vessel 208 and the ambient environment surrounding outervessel 208.

Inner vessel 206 comprises a sleeve (222), and outer vessel 208comprises a sleeve (221). Sleeve 221 of outer vessel extends withinsleeve 222 of inner vessel into cryogen space 203, such that insulationspace 210 extends between the sleeves.

Inner vessel 206 is supported within outer vessel 208 by supportstructures 212, which are designed to reduce thermal conduction betweenouter vessel 208 and inner vessel 206. These support structures 212 areshown, in FIG. 2 to be at the bottom of the vessel, however they may beany mechanical or structural component that supports outer vessel 208from inner vessel 206 and can be located at any location that providesadequate support of inner vessel 206 from outer vessel 208.

In this illustrated embodiment, pump assembly 204 includes pump 216operatively connected to pump drive unit 218, both fully disposed withinstorage receptacle 202. More specifically, pump assembly 204 is disposedwithin outer pump sleeve 222, located within cryogen space 203.Insulation space 210 thus provides thermal insulation between cryogenspace 203 and pump assembly 204 (except the portion of pump assembly 204that extends into cryogen space 203), and more specifically, thermalinsulation between pump drive unit 218 and cryogen space 203, tominimize any transfer of heat generated by pump drive unit 218 to thefluid stored within cryogen space 203, to prevent undesirablevaporization and venting.

In the illustrated embodiment still, pump assembly 204 is fully locatedwithin storage receptacle 202, such that pump drive unit 218 does notextend beyond covering 250, which connects with the top of outer vessel208 and covers pump assembly 204. In this arrangement, storagereceptacle 202 can be made larger, such that space 230, corresponding toempty space 112 in FIG. 1, is incorporated as part of cryogen space 203,increasing the total storage volume available for cryogenic fluid (whencompared to the total storage volume available for cryogenic fluid whenpump drive unit 218 is located entirely outside storage receptacle 202,and more specifically, outside outer vessel 208).

In other embodiments (not illustrated), locating pump drive unit 218only partially within storage receptacle 202 can still provide a morecompact arrangement compared to previously known arrangements thatlocate the entire pump drive unit 218 outside of outer vessel 208.

In an exemplary embodiment, pump 216 is a reciprocating piston pump thathas pump inlet 220 located toward the bottom of storage receptacle 202within cryogen space 203. Pump 216 is shown immersed in cryogen space203. This allows pump 216 to be maintained at the temperature of thestored cryogenic fluid, such that pump 216 does not need to be cooled tocryogenic temperatures before operation. In an exemplary embodiment,pump drive unit 218 is a hydraulically driven drive unit, howevernumerous other drive units may be substituted based on the applicationrequirements. By way of example, these substitute drive units mayinclude pneumatic drivers, mechanical drivers and electric motors.

A detailed view of drive unit 218 is shown in FIG. 3. Specifically, FIG.3 illustrates a detailed view of a hydraulic drive unit, 318. Hydrauliccylinder 301 is shown, within which piston 302 is disposed. Piston 302is hydraulically driven, and reciprocates by directing pressurizedhydraulic fluid to opposite sides of piston 302 in an alternatingfashion, producing reciprocating linear motion.

Specifically, pressurized hydraulic fluid flows from a hydraulic fluidreservoir (not shown) into hydraulic cylinder 301 in the direction shownby arrow A, via a high pressure conduit herein referred to as firsthydraulic fluid line 305, filling first hydraulic chamber 330. Thepressurized hydraulic fluid exerts a force on piston 302 causing piston302 to move downwards, in the direction shown by arrow A.Simultaneously, pressurized hydraulic fluid is pushed out of secondhydraulic chamber 332 to the hydraulic fluid reservoir via secondhydraulic fluid line 312, in the direction shown by arrow B. Secondhydraulic chamber 332 extends annularly around drive shaft 309.

Hydraulic drive unit 318 comprises one or more valves (not shown, and inother embodiments may be separate from the hydraulic drive unit) thatare actuated when piston 302 completes its stroke, such that at the endof the piston stroke, pressurized hydraulic fluid now enters secondhydraulic chamber 332 via second hydraulic fluid line 312, pushing thepiston upwards (opposite the direction shown by arrow A), forcing thepressurized hydraulic fluid out of first hydraulic chamber 330 to thehydraulic fluid reservoir, via first hydraulic fluid line 305.

Drive shaft 309 is rigidly connected to piston 302, and operativelyconnects pump 216 to drive unit 218 (318 in the case of a hydraulicdrive unit), such that as piston 302 and drive shaft 309 reciprocate,pump 216 is actuated. In an exemplary embodiment, pump 216 is areciprocating piston pump, such that drive shaft 309 extends betweenhydraulic drive unit 318 and pump 216, and as drive shaft 309reciprocates, drive shaft 309 actuates the piston in pump 216 toreciprocate.

Any hydraulic fluid that leaks along drive shaft 309 past shaft seals320 within end plate 306 is collected via another fluid line, hereinreferred to as weep line 310. Weep line 310 is located within endplate306, with an opening to the bore within which drive shaft 309reciprocates, to collect hydraulic fluid that leaks past shaft seals320, thus preventing leaked hydraulic fluid from collecting in thesleeve that extends to the pump.

This leaked hydraulic fluid is directed outside pump housing 307 viaweep line outlet 316 and returned to the hydraulic fluid reservoir.Hydraulic drive units are conventionally designed to minimize fluidleakage from within hydraulic cylinder 301. Thus, the hydraulic fluidthat leaks past shaft seals 320 is usually a small quantity at a slow,intermittent, flow rate. This low-flow leaked hydraulic fluid is incontact with the walls of weep line 316, and is exposed to cryogenictemperatures for a longer period of time than the faster flowing highpressure hydraulic fluid that travels through second hydraulic fluidline 312, and is thus more prone to freezing.

In conventional prior art systems with pump drive unit 218 outsidestorage receptacle 202, weep line 310 (and the low flow leaked hydraulicfluid that travels within it) is exposed to ambient temperatures, and isthus not prone to freezing. To prevent leaked hydraulic fluid fromfreezing within weep line 310 when pump drive unit 218 is located withinstorage receptacle 202, weep line 310 is located within pump housing307, and specifically nested within second hydraulic fluid line 312 toinsulate the intermittent and/or low-flow leaked hydraulic fluid withinweep line 310, from the surrounding cryogenic temperatures. Thecontinuous flow of high temperature hydraulic fluid within secondhydraulic fluid line 312 reduces heat transfer away from weep line 310,thus preventing the leaked hydraulic fluid from freezing.

While particular elements, embodiments and applications of the presentlyclaimed system have been shown and described, it will be understood thatexemplary embodiments are disclosed herein as examples of the claimedconcepts and described features, and the claimed system is not limitedthereto since variations for practicing the same concepts can be madewithout departing from the scope of the present disclosure, particularlyin light of the foregoing teachings.

The invention claimed is:
 1. A fluid storage and pressurizing assemblycomprising: a. a storage receptacle having an inner vessel defining acryogen space for storing fluid at a storage pressure and a cryogenictemperature, an outer vessel surrounding the inner vessel, and aninsulated space between the inner vessel and the outer vessel, and b. apump assembly further comprising: i. a pump drive unit at leastpartially disposed within a space defined by the storage receptacle,said pump drive unit separated from the cryogen space by thermalinsulation; and ii. a pump, actuatable by said pump drive unit, whichextends into and is immersed in the cryogen space thereby allowing thepump to be maintained at the temperature of the stored fluid when saidfluid is stored within said cryogen space, the pump having an inlet forreceiving a quantity of the fluid from the cryogen space and an outletfor delivering the fluid therefrom.
 2. The storage and pressurizingassembly of claim 1, wherein the pump drive unit is fully recessedwithin a sleeve of the outer vessel.
 3. The storage and pressurizingassembly of claim 1, wherein the pump drive unit is substantiallysurrounded by the cryogen space.
 4. The fluid storage and pressurizingassembly of claim 1, wherein the inner vessel comprises a sleeveextending into the cryogen space within which the pump drive unit is atleast partially disposed.
 5. The fluid storage and pressurizing assemblyof claim 4, wherein the pump drive unit is fully recessed within thesleeve extending into the cryogen space.
 6. The fluid storage andpressurizing assembly of claim 1, wherein the outer vessel comprises asleeve extending into the cryogen space within which the pump drive unitis at least partially disposed.
 7. The fluid storage and pressurizingassembly of claim 6, wherein the pump drive unit is fully recessedwithin the sleeve extending into the cryogen space.
 8. The fluid storageand pressurizing assembly of claim 1, wherein the inner vessel and outervessel each further comprise a sleeve, with the sleeve of the outervessel extending within the sleeve of the inner vessel into the cryogenspace.
 9. The fluid storage and pressurizing assembly of claim 8,wherein the pump drive unit is at least partially disposed within thesleeve of the outer vessel.
 10. The fluid storage and pressurizingassembly of claim 8, wherein the pump drive unit is fully disposedwithin the sleeve of the outer vessel.
 11. The fluid storage andpressurizing assembly of claim 8, whereby the insulated space extendsbetween the sleeve of the outer vessel and the sleeve of the innervessel.
 12. The storage and pressurizing assembly of claim 11, whereinthe insulated space is an evacuated space.
 13. The fluid storage andpressurizing assembly of claim 1, wherein the pump is a reciprocatingpiston pump comprising at least one piston disposed within a pumpcylinder.
 14. The fluid storage and pressurizing assembly of claim 13,wherein the reciprocating piston pump pressurizes the fluid to apressure between 2500 psi-9500 psi.
 15. The fluid storage andpressurizing assembly of claim 1, wherein the thermal insulationseparating the pump drive unit from the cryogen space includes anevacuated space.
 16. The fluid storage and pressurizing assembly ofclaim 1, wherein the pump drive unit is an electric motor.
 17. The fluidstorage and pressurizing assembly of claim 1, wherein the pump driveunit is a hydraulic drive unit having a hydraulic cylinder and a pistonreciprocable therein, and a drive shaft connected with the pistonextending out of the hydraulic cylinder for actuating the pump.
 18. Thefluid storage and pressurizing assembly of claim 17, further comprisinga hydraulic fluid weep line associated with the drive shaft forcollecting hydraulic fluid leaking from the hydraulic cylinder along thedrive shaft.
 19. The fluid storage and pressurizing assembly of claim18, wherein the hydraulic fluid weep line is at least partially nestedwithin another hydraulic fluid line.
 20. The fluid storage andpressurizing assembly of claim 1, wherein the pump drive unit is amechanical drive or a pneumatic drive.